If a car battery is working well, we tend to forget it exists. But if it stops working, do you know how to disconnect it and replace it safely? Learn how here.
Time 0.5 to 2 hours
ComplexityBeginner
CostVaries
Introduction
Pretty much anyone who drives a gas-powered automobile has had the following experience: When you try to start your vehicle, you hear a clicking sound — and that’s it. The battery is dead, and there’s not enough juice to power the starter.
In most cases, you can simply get a jump from a neighbor or from road service, but if something like this happens repeatedly, it’s a sign that you need to replace the battery. To do this, you need to know how to disconnect a battery. It’s not a particularly dangerous operation if the battery is dead, but if you have to do it while the battery still has plenty of juice, the danger increases. Shorting battery terminals can be a shocking experience, and not in a good way.
These car battery tips, informed by mechanic Bryan Jewett, can help you disconnect a battery quickly and safely.
Tools Required
- Acid-resistant gloves
- Cup style wire cleaning brush
- Pipe cleaning wire brush
- Safety glasses
- Wrench (typically 10 mm
Materials Required
- Anti-corrosion grease (optional)
- Anti-rust spray (optional)
- Heavy-duty shop towels
Project step-by-step (5)
Step 1
Shut everything off and find the battery
- Make sure your vehicle is not running and all electrical components are off before starting the battery disconnection process.
- Open your vehicle’s hood if that’s where the battery is housed, as it is in most vehicles. If your battery is somewhere else, do whatever you need to do to gain access.
- Remove the red plastic cover from the battery’s positive terminal.
Step 2
Disconnect the battery cables
Safety first: When you disconnect a battery, always disconnect the negative terminal first to reduce the risk of short-circuiting, says Jewett.
- Use your socket wrench or adjustable wrench to loosen the nut holding the cable onto the negative battery terminal. The terminals will be marked positive and negative. Make sure you disconnect the negative terminal first.
- Lay the disconnected negative cable carefully to one side, making sure it’s well away from the battery terminal.
- Disconnect the cable from the positive battery terminal in the same way, then lay it to one side.
Pro tip: While loosening the cables, be sure not to touch your wrench to both terminals at the same time. This will allow electricity from the battery to flow through your wrench.
Step 3
Remove the battery
- Find the strap or other mechanism holding your battery in place. On my vehicle it is a steel strut that caps the top of the battery. Use the appropriate wrench to loosen and remove this.
- Carefully lift the battery out of the vehicle, making sure to keep it level the whole time to avoid sloshing the acid inside.
- Lay the battery on a flat surface away from the vehicle.
Pro tip: “Car batteries are heavy and can leak acid,” says Garrett Tortelli of Batteries Plus, “so always carry them upright and store them in a ventilated, dry area.”
Step 4
Clean the terminals and cable contacts
- Use your pipe cleaning-style wire brush to carefully clean the inner surface of the battery cable connectors where they contact the terminals. This surface should be smooth and free of corrosion before installing your new battery.
- Clean the battery terminals with the cup-style wire brush, making sure the terminals are free of corrosion and debris.
- To help prevent new rust from forming, apply a little anti-corrosion grease to the battery terminals with your fingers. Wipe off the excess from your fingers with a heavy-duty shop towel.
Step 5
Reinstall the battery
- If you are concerned about rust, spray some anti-rust compound onto the metal platform where the battery sits. This isn’t necessary, but if the platform is exposed steel, it may rust in time if it hasn’t already.
- Lift your new battery (or the old one, if it’s still good) back into position on its platform.
- Replace the containment strap or strut over the battery, and tighten the nuts holding it down as required.
- Reconnect the positive cable to the positive terminal, making sure it’s tight.
- Reconnect the negative cable to the negative battery terminal in the same way, and you’re done.
- Reset the digital clock in your vehicle, because whenever you disconnect a car battery, it loses power. It will no longer be showing the correct time.
About the Experts
- Bryan Jewett is the Owner and Operator of Casey’s Automotive in Chantilly, VA.
- Garrett Tortelli is the Senior Merchandise Manager at Batteries Plus.
